The fastening of an object on a support is frequently brought about with the aid of a device utilizing a screw and a nut.
This is the case especially for the fastening of a toilet seat (cover) on a water closet (bowl). In this case, the device contains a threaded rod whose head bears on the fixed part of the seat, traverses it, and then goes through a hole which is cut in the bowl. A nut is screwed on the threaded rod, which in turn goes on to press on the bottom side of the bowl, thus fixing of the assembly.
The inconvenience of such a process is the fact that the maneuvers required for screwing are difficult due to bad accessibility to the parts which have to be handled.